In general, a vehicle security system may operate in several ways to discourage the theft of a vehicle or the tampering with the contents therein. For example, a vehicle security system may operate to control ignition disablement, sound a theft triggered alarm, or both of these.
In one type of a vehicle anti-theft system, a receiver is mounted in the trunk of an automobile. The receiver is connected to the electrical system of the automobile, and when the system is "armed" the ignition system is disabled from operating. In order to operate the vehicle, a hand held transmitter is operated at the same time that the ignition system of the vehicle is turned on. The receiver recognizes the coded signal and inhibits further disablement of the ignition system. The system is armed automatically whenever the ignition is turned off. A key operated switch on the receiver is provided to allow the driver to deactivate the anti-theft system when such deactivation is desired. For example, one would deactivate the system when the car is parked by attendants with whom the key is left in a public garage.
It would appear that the automatic arming feature is a desirable one in that no action is required on the part of the operator to arm the system. The security controls of the anti-theft system are put into effect automatically when the ignition system is turned off. However, the automatic arming feature also has a significant disadvantage and limitation. This disadvantage and limitation may outweigh any of the advantages of the automatic arming feature in many cases.
For example, there are many times when an operator does not want to arm the anti-theft system. For example, the operator may desire to remain nearby the automobile and would accordingly not desire to be bothered by having to operate the transmitter in order to enable the ignition system upon the return to the vehicle. Another example is where the anti-theft system is equipped with an audible alarm which sounds in response to an attempt being made to gain unauthorized access to the vehicle. It is apparent that such a feature, the automatic arming, could pose a problem.
With automatic arming, the driver must be given time to leave the vehicle before the alarm system is enabled. Otherwise, when he opens the door in order to exit the vehicle, the alarm will be triggered. It is standard practice, therefore, in the case of vehicles having alarm systems which are automatically armed, to delay the arming of the system for a short time after the ignition is turned off, for example, thirty seconds. Conversely, a second delay, of perhaps fifteen seconds, is required to allow the authorized operator to re-enter the vehicle upon his return and disarm the system. The problem with this approach is that a trained automobile thief can foil the system before the short time delays have elapsed.
The use of time delays for ingress and egress from the vehicle while the alarm system is armed has been eliminated by the use of the transmitter, not only to disarm the system upon returning to the automobile, but also to arm it after leaving, as soon as the driver shuts and locks the door and is walking away from the vehicle. He may operate the transmitter at any time within the vicinity of the vehicle to arm or disarm the system.
This type of system has the advantage in that it will foil an attempt by any thief to enter the automobile after the driver has left and before the arming delay interval has expired. One prior art alternative to accomplishing this object is to provide a key operated switch on the outside of the vehicle itself, and it is certainly far easier to push a transmitter button in ones pocket than it is to take out and use a key for arming a system as is customary practice, not to mention that such a key switch is vulnerable to expert assault.
Furthermore, when the ignition system of the vehicle is on, the system may not be armed if the transmitter is activated to develop the encoded signal. The purpose of this feature is to prevent the disabling of the vehicle, such as by ignition cut off, when the vehicle is being operated and the transmitter inadvertently activates the receiver. However, a disadvantage and limitation of this feature is that when the user wants to leave the car shortly, for example, to make a telephone call, and keep the engine running, the system may not be armed. Yet another example when it is desirable to keep the engine running or at least keep the ignition system of the vehicle on, is when the operator wishes to pull into a rest stop and sleep inside the automobile and keep the radio or air conditioning operating, the above anti-theft system could not be armed while continuing to protect the car. Therefore, it is highly desirable to provide a security system which has both a theft deterrent and an occupant protection feature.